Various types of co-ordinate measuring machines are known: bridge machines, horizontal-arm machines, pillar machines, etc. Each of these machines typically comprises a reference surface, a first carriage mobile with respect to the reference surface along a first axis, a second carriage carried by the first carriage and mobile with respect thereto along a second axis perpendicular to the first, and a measuring spindle carried by the second carriage and mobile with respect thereto along a third axis perpendicular to the first and second axes. The spindle is designed to carry a measuring tool, which is displaced in the measuring volume as a result of the combination of the motions along the three axes.
For example, in bridge measuring machines, the first carriage is mobile along a horizontal axis and comprises two uprights and a horizontal cross member that defines the second axis, which is also horizontal. In the aforesaid machines, also the spindle is constituted by a beam element with vertical axis, mounted so that it can slide along its own axis. The various beam elements of a measuring machine, for example the spindle and the cross member of a bridge machine of the type briefly described, must satisfy mutually antithetic requirements.
From a structural standpoint, it is necessary for each element of a measuring machine to be as stiff as possible so as to limit the measuring errors caused by the elastic deformations of the structures. However, the mobile parts of the machine must be as light as possible so as to reduce the dynamic stresses. Finally, it is necessary for said elements to be machinable so as to enable the necessary machining operations, for example, to obtain the sliding surfaces with high surface finish that are necessary for relative motion of the parts.
In known machines, beam elements are generally made of an aluminium alloy, by casting or extrusion. Known techniques and materials generally enable acceptable compromise solutions to be obtained between the required properties. The need for further improvements is, however, felt in the sector.